std::thread_local!

macro_rules! thread_local {
    (static $name:ident: $t:ty = $init:expr) => (
        static $name: $crate::thread::LocalKey<$t> =
            __thread_local_inner!($t, $init,
                #[cfg_attr(all(any(target_os = "macos", target_os = "linux"),
                               not(target_arch = "aarch64")),
                           thread_local)]);
    );
    (pub static $name:ident: $t:ty = $init:expr) => (
        pub static $name: $crate::thread::LocalKey<$t> =
            __thread_local_inner!($t, $init,
                #[cfg_attr(all(any(target_os = "macos", target_os = "linux"),
                               not(target_arch = "aarch64")),
                           thread_local)]);
    );
}

Declare a new thread local storage key of type std::thread::LocalKey.

See LocalKey documentation for more information.